Electric arc welding method



United States Patent Ofiice 3,047,708 Patented July 31, 1962 3,047,708ELECTRIC ARC WELDING METHOD Louis E. Stark, Youngstown, Ohio, assignorto Union Carbide Corporation, a corporation of New York No Drawing.Original application Dec. 12, 1957, Ser. No. 702,235. Divided and thisapplication Dec. 18, 1959, SeY. No. 860,360

3 Claims. (Cl. 219-74) This invention relates to a welding flux powderand more particularly to an essentially non-magnetic welding flux powderwith a magnetic coating especially suited for use in gas shielded,consumable electrode arc welding and to a method of producing same.

This application is a division of my co-pending application Serial No.702,235 filed December 12., 1957.

The term magnetic material as used herein is intended to apply to amaterial which is attracted to a magnet or especially to a wireelectrode having a surrounding magnetic field created by an electriccurrent flowing through the wire. A non-magnetic material herein is onewhich is substantially not attracted by a magnetic flux field.Magnetization as used herein means the attachment to normallynon-magnetic powder particles of a magnetic component.

In electric arc welding wherein an alloy Weld metal is produced on ametal workpiece by means of a gas shielded, bare, consumable electrodeand a magnetic alloy powder, the magnetic alloy powder is prepared bymixing the crushed alloy powder in a desired composition ratio with asuitable amount of magnetic powder, such as iron, nickel or cobalt.Bonding of the mixture is generally accomplished with sodium silicatesolution followed by drying and recrushing.

While the aforesaid magnetic alloy powder is for the most partsatisfactory, problems have arisen in powders so formed. In manyinstances, careful recrushing of the bonded mixture is necessary inorder to assure that all the agglomerate particles contain sufiicientmagnetic material. Otherwise, the particles fall free of the electrodeout of the weld zone, or enter the outer edges of the weld puddlewithout sufiicient time for complete solution in the weld. The loss ofthese powder particles reduces therecovery of alloy in the weld deposit.In addition, the sodium silicate, which is not assimilated in the weldmetal causes the formation of surface splinters or shards which detractfrom the appearance of the weld.

It is, therefore, an important object of the present invention toprovide an economical method of rendering a non-magnetic materialmagnetic.

Another object is to provide an improved electric arc welding powdercontaining a magnetic component in the particles thereof.

Another object of the present invention is to provide an improvedelectric arc welding powder capable of being used in the standardmagnetic coating welding processes, such as Unionarc and Sigmaloywelding processes, the powder comprising non-magnetic particles havingmagnetic coatings.

Another object of the present invention is to pr vide an improvedwelding powder capable of produc ing on a metal workpiece a weld deposithaving essentially the same properties as a weld deposit made fromsodium silicate bonded powders, yet producing a weld free of surfaceblemishes.

Another object of the present invention is to provide an improvedwelding powder wherein the need for the slag or gas-forming constituentsof a binder and the need for subsequent recrushing and sizing operationsare substantially reduced or eliminated.

Another object of the present invention is to provide in theincorporation of powder in the weld metal in fusible electrode arcwelding, an improved method for adding non-magnetic material withoutloss.

The present invention is based on my discovery that non-magnetic powdersmay be made magnetic by plating or coating with a magnetic material. Thenon-magnetic materials include powdered fluxing ingredients, powderedmetal or alloying mixtures substantially free of fiuxing ingredients, orany combination thereof.

In accordance with my invention, magnetization of a non-magnetic,welding powder material is accomplished by plating the non-magneticmaterial with a thin coating of a magnetic material. Among the magneticcoating materials which have proved satisfactory are iron, 00- balt andnickel. These coating materials may also serve as specific metaladditives to the weld. Economic considerations make iron the mostdesirable of these. For satisfactory results the coating materialsshould be present at least in an amount between about 3.5 percent and 10percent by weight of welding powder, depending, of course, upon thespecific coating material employed.

Any of a number of non-magnetic or slightly magnetic powdered metalconstituents may be used as core particles in the magnetic weldingpowder of the invention. Elements such as aluminum, chromium, manganese,silicon, carbon, tungsten, molybdenum, columbium, magnesium, and copperare conventional ingredients in welding powders. Alloying ingredientssuch as high carbon ferrochromium, low carbon ferrochromium,ferromanganese, ferrosilicon, ferrotungsten, graphite and tungstencarbide have also proved useful as core ingredients in the invention.

The coated magnetic powder embodying the principles of the invention maybe made by suitably comminuting the desired non-magnetic ingredients toapproximately 35 D mesh size (i.e., capable of passing-through a screenhaving 0.417 mm. openings), and then immersing the comminutedingredients into an electrolyte solution to be electroplated in theusual manner. The electrolyte solution is provided with conventionalcathode and anode electrodes connected to a source of power, a suitableanode being employed to replace the iron, nickel, or cobalt ions whichserve to plate the surfaces of the non-magnetic powders. A preferredelectrolyte is ferrous chloride, and a preferred anode is iron.Thereafter a suitable voltage is impressed across the solution for asufficient length of time to satisfactorily coat the comminutedingredients.

In order to indicate still more fully the nature of the presentinvention, the following typical example of the invention is set forth,it being understood that the data presented therein are illustrativeonly, and not intended to limit the scope of the invention.

Example Six hundred ninety-three grams of high carbon chromium powdercomminuted to approximately 35 X 325 mesh size (i.e., capable of passingthrough a screen having 0.417 mm. openings but being retained on ascreen having 0.43 mm. openings), was electroplated with iron in 2900cc. of an aqueous solution containing 968 grams of ferrous chloride(FeCl -4H O) and 975 grams of calcium chloride (CaC1 Electroplating wasconducted at from 6 /2 to 9 volts at a current of 46 amperes for 230ampere hours. The weight of the granular material increased from 693grams to 911.8 grams due to the iron coating formed on the discreteparticles. Analysis of the powdered material before and afterelectroplating was, as follows:

Fe, percent In In welding according to the teaching of the invention,essentially no powder loss occurred due to the powder particles beingindividually magnetic. Chemical analysis of weld deposits showed verygood alloy recovery. In addition, welds made with the welding powder ofthe invention were free of surface slag and had good edges and contours.

From the foregoing description, it will be apparent to those skilled inthe art that the invention provides a novel magnetic welding powder, theparticles of which have a core of substantially non-magnetic materialand a coating of a magnetic material. The magnetic powder of theinvention is eminently suited to use in electric arc welding of theUnionarc and Sigmaloy welding type, which the adherence of a metalpowder or a fiuxing powder to bare wire electrode, due to themagnetizable property of the powder and the magnetic field surroundingthe electrode, isrequired. Further, it will be evident that theinvention encompasses a number of combinations and that thosespecifically discussed herein are described for purposes of illustratingthe principles of the invention and not for limiting its scope.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the invention.

What is claimed is:

1. An electric arc welding method in which a consumable electrode isconnected to a source of welding current which comprises: advancing theconsumable electrode toward a workpiece, passing a welding currentthrough the electrode to establish a magnetic flux thereabout and toform an electric are at the workpiece, directing a stream of shieldinggas along the electrode and towards the said arc, feeding toward saidelectrode a powdered Welding 4 material composed of particles of anon-magnetic welding material having on the outer surface thereof acoating consisting of a layer of a magnetic metal whereby said powderedwelding material will be magnetically drawn to the electrode andconveyed thence to the weld area as the electrode is advanced thereto.

2. An electric arc method substantially as described in claim 1 whereinthe powdered welding material consists of particles of at least one ofthe materials chosen from the group consisting of high carbonferrochromium, low carbon ferrochromium, ferromanganese, ferrosilicon,ferrotungsten, graphite and tungsten carbide, said particles having anouter layer consisting of a coating of a magnetic metal chosen from thegroup consisting of iron, cobalt, and nickel.

3. An electric arc welding method in which a consumable electrode isconnected to a source of welding cur, rent which comprises: advancingthe consumable electrode toward a workpiece, passing a welding currentthrough the electrode to establish a magnetic field thereabout and toform an electric arc with the workpiece, directing a stream of shieldinggas along the electrode and toward the said are, feeding toward theelectrode a powdered welding flux composed of coated particles of atleast one non-magnetic welding flux material from the group consistingof aluminum, chromium, manganese, silicon, carbon, tungsten, molybdenum,columbium, magnesium, and copper, said particle having as an outer layera coating of a magnetic metal from the group consisting of iron, cobalt,and nickel, whereby said coated particle will be magnetically drawn tothe electrode and conveyed thence to the workpiece.

References Cited in the file of this patent UNITED STATES PATENTS2,003,040 Strobel May 28, 1935 2,021,040 Zublin Nov. 12, 1935 2,507,400Marinis May 9, 1950 2,644,787 Bonn et al. July 7, 1953 2,805,323 CushmanSept. 3, 1957 2,868,949 Todd Jan. 13, 1959 2,947,847 Craig et a1. Aug.2, 1960 2,948,803 Wilson et al, Aug. 9, 1960

